WO2015152090A1 - Carbonaceous material for negative electrodes of nonaqueous electrolyte secondary batteries, negative electrode for nonaqueous electrolyte secondary batteries, nonaqueous electrolyte secondary battery and vehicle - Google Patents

Abstract

To provide: a carbonaceous material for negative electrodes of nonaqueous electrolyte secondary batteries, which provides a negative electrode for nonaqueous electrolyte secondary batteries having excellent input/output characteristics; a negative electrode for nonaqueous electrolyte secondary batteries, which has a high discharge capacity per volume; a nonaqueous electrolyte secondary battery which is provided with this negative electrode for nonaqueous electrolyte secondary batteries; and a vehicle. A carbonaceous material for negative electrodes of nonaqueous electrolyte secondary batteries according to the present invention has a number average particle diameter of 0.1-2.0 μm, and the value obtained by dividing the number average particle diameter by the volume average particle diameter is 0.3 or less. This carbonaceous material for negative electrodes of nonaqueous electrolyte secondary batteries has an average plane spacing (d₀₀₂) of the (002) plane of 0.340-0.390 nm as determined by an X-ray diffraction method and an atomic ratio of hydrogen to carbon (H/C) of 0.10 or less.

Description

Non-aqueous electrolyte secondary battery negative electrode carbonaceous material, non-aqueous electrolyte secondary battery negative electrode, non-aqueous electrolyte secondary battery and vehicle

The present invention relates to a carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode, a negative electrode for a nonaqueous electrolyte secondary battery, a nonaqueous electrolyte secondary battery, and a vehicle.

In recent years, due to increasing interest in environmental problems, mounting of large-sized lithium ion secondary batteries with high energy density and excellent output characteristics to electric vehicles has been studied. In small portable devices such as mobile phones and notebook computers, capacity per volume is important, and thus a graphite material having a high density has been mainly used as a negative electrode active material. However, in-vehicle lithium ion secondary batteries are large and expensive, and are difficult to replace in the middle. For this reason, the same durability as that of an automobile is required, and for example, realization of a life performance of 10 years or more (high durability) is required.
Also, with regard to the usage form of the secondary battery, for example, in a power source for a hybrid vehicle, which is 1 to 2 hours in a small portable device, taking into account energy regeneration during braking, it is several tens of seconds. Considering the time to depress the accelerator, the discharge is required for rapid charge / discharge (input / output) characteristics that are overwhelmingly superior to lithium ion secondary batteries for small mobile phones.
Conventionally, carbonaceous materials obtained by carbonizing organic materials and plant raw materials have been usefully used as negative electrodes for lithium ion secondary batteries. However, as described above, carbon for negative electrodes used for in-vehicle lithium ion secondary batteries is used. The material is required to have excellent charge / discharge characteristics, and improvement of the input / output characteristics is indispensable for realizing it.

So far, in order to improve the input / output characteristics, it has been studied to secure a gap between the negative electrode active materials in the negative electrode of the non-aqueous electrolyte secondary battery. For example, as a method for ensuring a gap between the negative electrode active materials, a spherical non-graphitizable carbonaceous material is used for the negative electrode to improve output characteristics and charge / discharge capability (Patent Document 1), and an appropriate electrode density. Although a device that improves the input / output characteristics by setting to a small value (Patent Document 2) is described, the input / output characteristics are not sufficient. Moreover, in order to ensure the space | gap between particles of an active material, the carbonaceous material by which particle shape and particle size distribution were adjusted is proposed (patent document 3).

International Publication No. 2005/098998 JP 2002-334893 A International Publication No. 2013/118757

However, in-vehicle lithium ion secondary batteries are required to further improve input / output characteristics including discharge capacity per volume in order to extend the cruising distance with one charge and further improve vehicle fuel efficiency. In consideration of the fact that automobiles are used in cold regions, it is required to maintain high input characteristics even in a low temperature environment.

An object of the present invention is to provide a carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode that provides a negative electrode for a nonaqueous electrolyte secondary battery having excellent input / output characteristics, and a negative electrode for a nonaqueous electrolyte secondary battery having a high discharge capacity per volume. Another object is to provide a nonaqueous electrolyte secondary battery and a vehicle including the negative electrode for the nonaqueous electrolyte secondary battery.

In the carbonaceous material having a small number particle diameter of 0.1 to 2.0 μm and having a number average particle diameter of 0.1 to 2.0 μm, a value obtained by dividing the number average particle diameter by the volume average particle diameter is 0.3 or less. It has been found that the input / output characteristics can be rather improved by adopting a simple particle size distribution, and the present invention has been completed. Specifically, the present invention provides the following.

(1) The number average particle diameter is 0.1 to 2.0 μm, the value obtained by dividing the number average particle diameter by the volume average particle diameter is 0.3 or less, and the (002) plane determined by the X-ray diffraction method A carbonaceous material for a negative electrode of a nonaqueous electrolyte secondary battery having an average layer surface spacing d ₀₀₂ of 0.340 to 0.390 nm and an atomic ratio (H / C) of hydrogen and carbon of 0.10 or less.

(2) The carbonaceous material for a negative electrode of a nonaqueous electrolyte secondary battery according to (1), wherein the volume average particle diameter _Dv50 is 1 to 7 μm.

(3) The carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode according to the above (1) or (2), wherein the cumulative volume particle diameter _Dv10 is 2.5 μm or less.

(4) The carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode according to any one of (1) to (3) above, wherein the amount of particles having a particle diameter of 30 μm or more is 1.0% by volume or less.

(5) A negative electrode for a nonaqueous electrolyte secondary battery comprising the carbonaceous material for a negative electrode for a nonaqueous electrolyte secondary battery according to any one of (1) to (4) above.

(6) The negative electrode for a non-aqueous electrolyte secondary battery according to (5), wherein the electrode density is 1.02 g / cm ³ or more when a pressing pressure of 13 MPa (2.5 tf / cm ² ) is applied.

(7) The negative electrode for a nonaqueous electrolyte secondary battery according to (5) or (6) above, wherein the average thickness is 60 μm or less.

(8) A nonaqueous electrolyte secondary battery comprising the negative electrode for a nonaqueous electrolyte secondary battery according to any one of (5) to (7) above.

(9) A vehicle equipped with the nonaqueous electrolyte secondary battery described in (8) above.

According to the present invention, the number average particle diameter is 0.1 to 2.0 μm, and the value obtained by dividing the number average particle diameter by the volume average particle diameter is 0.3 or less, which is determined by the X-ray diffraction method ( By using a carbonaceous material having an average layer spacing d ₀₀₂ of (002) plane of 0.340 to 0.390 nm and an atomic ratio (H / C) of hydrogen and carbon of 0.10 or less, the input / output characteristics are improved. An excellent negative electrode is provided. In particular, a negative electrode having good input characteristics under a low temperature environment and a high discharge capacity per volume can be obtained.

Hereinafter, embodiments of the present invention will be described.

[1] Carbonaceous material for negative electrode of nonaqueous electrolyte secondary battery The carbonaceous material for negative electrode of nonaqueous electrolyte secondary battery of the present invention has a number average particle size of 0.1 to 2.0 μm and a number average particle size of The value divided by the volume average particle diameter is 0.3 or less, the average layer spacing d _{002 of} (002) plane determined by X-ray diffraction method is 0.340 to 0.390 nm, and the atomic ratio of hydrogen and carbon (H / C) is 0.10 or less.

The carbonaceous material having a number average particle diameter of 0.1 to 2.0 μm and a value obtained by dividing the number average particle diameter by the volume average particle diameter is 0.3 or less, the small particle diameter particles are rich and Has a broad particle size distribution. Since such a carbonaceous material can be closely packed, it is easy to produce a negative electrode having a high amount of active material per volume and a high charge / discharge capacity per volume.

The average layer spacing of the (002) plane of the carbonaceous material shows a smaller value as the crystal perfection is higher, that of an ideal graphite structure shows a value of 0.3354 nm, and the value increases as the structure is disturbed. Tend. Therefore, the average layer spacing is effective as an index indicating the carbon structure. In the present invention, the average layer spacing d ₀₀₂ of the (002) plane obtained by the X-ray diffraction method is 0.340 to 0.390 nm. The carbonaceous material having a graphite structure whose d ₀₀₂ is less than 0.340 nm is used in a secondary battery using such a carbonaceous material as a negative electrode material. And the electrolytic solution is easily decomposed, and the charge / discharge cycle characteristics of the battery are inferior. In addition, a carbonaceous material having d ₀₀₂ exceeding 0.390 nm increases the irreversible capacity of an active material such as lithium, and decreases the utilization rate of the active material. In this respect, d ₀₀₂ is preferably 0.340 to 0.390 nm. The lower limit is more preferably 0.345 nm and even more preferably 0.350 nm. Moreover, the upper limit is more preferably 0.385 nm or less.

A carbonaceous material having d ₀₀₂ of 0.365 nm or more (particularly 0.370 nm or more) and 0.390 nm or less is called so-called hard carbon (non-graphitizable carbon), and d ₀₀₂ is 0.345 to 0.370 nm (particularly 0). .345 to 0.365 nm) is called so-called soft carbon (graphitizable carbon). The carbonaceous material of the present invention can be applied to any carbonaceous material, and can be densely packed by having the particle size distribution described above.

H / C of the carbonaceous material of the present invention is measured by elemental analysis of hydrogen atoms and carbon atoms. Since the hydrogen content of the carbonaceous material decreases as the degree of carbonization increases, H / C is It tends to be smaller. Therefore, H / C is effective as an index representing the degree of carbonization. Although H / C of the carbonaceous material of this invention is not limited, it is 0.10 or less, More preferably, it is 0.08 or less. Especially preferably, it is 0.05 or less. If the ratio H / C of hydrogen atoms to carbon atoms exceeds 0.1, many functional groups are present in the carbonaceous material, and the irreversible capacity may increase due to reaction with lithium, which is not preferable.

In the present invention, the volume average particle diameter of the carbonaceous material (D _v50) is too small, increased ultra-fine powder has high reactivity with a liquid electrolyte, since it tends to increase the irreversible capacity, D _v50 is It is preferable that it is 1 micrometer or more, More preferably, it is 2 micrometers or more. On the other hand, if the _Dv50 is excessive, the small particle size powder involved in improving the input / output characteristics described above tends to be insufficient, so the _Dv50 is preferably 7 μm or less, more preferably 6 μm or less. .

Cumulative volume particle diameter D _v10 of the carbonaceous material, suitably reflect the frequency at the end of small particles径粉. As described above, in the present invention, the small particle diameter carbonaceous powder contributes to the improvement of the input / output characteristics. Therefore, _Dv10 is 2.5 μm or less in that the small particle diameter carbonaceous powder is sufficiently contained. It is preferable that the thickness is 2.0 μm or less.

In the present invention, the fact that the carbonaceous material is densely packed contributes to the improvement of the input / output characteristics. If the cumulative volume particle diameter _Dv90 is excessive, small particles that contribute to the improvement of the input / output characteristics. _Dv90 is preferably 16 μm or less, more preferably 14 μm or less, because the amount of carbonaceous powder having a diameter tends to be insufficient.

As an index of particle size _{distribution, (D v90 -D v10) /} D v50 can be _{used, (D v90 -D v10) /} D v50 of the non-aqueous electrolyte secondary battery carbonaceous material of the present invention, a broad In view of giving a particle size distribution, 1.4 or more is preferable, and 1.6 or more is more preferable. However, since an excessively broad particle size distribution requires labor for pulverization and classification, the upper limit of (D _v90 -D _v10 ) / D _v50 is preferably 3 or less.

In the present invention, in order to improve the input / output characteristics, although not particularly limited, it is effective to make the active material layer of the negative electrode thin. Although the above carbonaceous material can be densely packed, the voids formed between the carbonaceous powders of the negative electrode are reduced, and the movement of lithium in the electrolytic solution is suppressed, affecting the output characteristics. However, when the active material layer of the negative electrode is thin, the diffusion process of lithium ions is shortened. As a result, the merit of increasing the capacity per volume is easily surpassed compared to the demerit that suppresses the migration of lithium due to close packing. Become. From the viewpoint of forming such a thin and smooth active material layer, it is preferable that a large amount of particles having a large particle diameter is not contained. Specifically, the amount of particles having a volume particle diameter of 30 μm or more is 1.0% by volume. Or less, more preferably 0.5% by volume or less, and most preferably 0% by volume. Such adjustment of the particle size distribution may be performed by classification after pulverization in the production process.

The true density (ρ _Bt ) determined by the butanol method may be 1.52 g / cm ³ or more and less than 2.10 g / cm ³ . When the carbonaceous material of the present invention has such a high true density, a higher capacity per volume can be exhibited. Specifically, ρ _Bt may be 1.52 g / cm ³ or more and 1.75 g / cm ³ or less, or 1.70 g / cm ³ or more and less than 2.10 g / cm ³ .

If the specific surface area (SSA) determined by the BET method of nitrogen adsorption of the carbonaceous material of the present invention is excessive, the irreversible capacity of the resulting battery tends to be large, so it may be 25 m ² / g or less. , Preferably 20 m ² / g or less. On the other hand, if the BET specific surface area is too small, the discharge capacity of the battery tends to be small, so that it is 1 m ² / g or more, preferably 3 m ² / g or more, more preferably 6 m ² / g or more.

The carbonaceous material for the non-aqueous electrolyte secondary battery negative electrode of the present invention is not particularly limited, but the grinding conditions and the like are controlled based on a manufacturing method similar to the conventional carbon negative electrode material for non-aqueous electrolyte secondary battery. Can be manufactured satisfactorily. Specifically, it is as follows.

(Carbon precursor)
The carbonaceous material of the present invention is produced from a carbon precursor. Examples of the carbon precursor include petroleum pitch or tar, coal pitch or tar, thermoplastic resin, or thermosetting resin. In addition, as the thermoplastic resin, polyacetal, polyacrylonitrile, styrene / divinylbenzene copolymer, polyimide, polycarbonate, modified polyphenylene ether, polybutylene terephthalate, polyarylate, polysulfone, polyphenylene sulfide, fluororesin, polyamideimide, or polyether Mention may be made of ether ketones. Furthermore, examples of the thermosetting resin include phenol resin, amino resin, unsaturated polyester resin, diallyl phthalate resin, alkyd resin, epoxy resin, and urethane resin.
In the present specification, the “carbon precursor” means a carbonaceous material from an untreated carbonaceous material stage to a pre-stage of a carbonaceous material for a nonaqueous electrolyte secondary battery finally obtained. That is, it means all the carbonaceous matter that has not finished the final process.

(Crosslinking treatment)
When petroleum pitch or tar, coal pitch or tar, or a thermoplastic resin is used as the carbon precursor, a crosslinking treatment is performed. The method for the crosslinking treatment is not particularly limited, and can be performed using, for example, an oxidizing agent. The oxidizing agent is not particularly limited, but as the gas, O ₂ , O ₃ , SO ₃ , NO ₂ , a mixed gas obtained by diluting these with air, nitrogen or the like, or an oxidizing gas such as air is used. Can do. As the liquid, an oxidizing liquid such as sulfuric acid, nitric acid, or hydrogen peroxide, or a mixture thereof can be used. The oxidation temperature is not particularly limited, but is preferably 120 to 400 ° C, and more preferably 150 to 350 ° C. When the temperature is less than 120 ° C., the crosslinking reaction does not proceed sufficiently, and a long time is required for the reaction. On the other hand, when the temperature exceeds 400 ° C., the decomposition reaction is more than the crosslinking reaction, and the yield of the obtained carbon material is lowered.

Calcination uses a carbon precursor as a carbonaceous material for a negative electrode of a nonaqueous electrolyte secondary battery. When pre-baking and main baking are performed, the temperature may be once lowered after the pre-baking, pulverized, and main baking may be performed. The pulverization step may be performed after the crosslinking treatment, but is preferably performed after preliminary firing.

The carbonaceous material of the present invention is produced by a step of pulverizing a carbon precursor and a step of firing the carbon precursor.

(Pre-baking process)
The pre-baking step in the present invention is performed by baking the carbon source at 300 ° C. or higher and lower than 900 ° C. Pre-firing removes volatile components such as CO ₂ , CO, CH ₄ , and H ₂ , and tar components, and reduces the generation of these components in the main firing, thereby reducing the burden on the calciner. . When the pre-baking temperature is less than 300 ° C., detarring becomes insufficient, and there is a large amount of tar and gas generated in the main baking process after pulverization, which may adhere to the particle surface. This is not preferable because it cannot be maintained and the battery performance is lowered. The pre-baking temperature is preferably 300 ° C. or higher, more preferably 500 ° C. or higher, particularly preferably 600 ° C. or higher. On the other hand, when the pre-baking temperature is 900 ° C. or higher, the tar generation temperature region is exceeded, and the energy efficiency to be used is lowered, which is not preferable. Furthermore, the generated tar causes a secondary decomposition reaction, which adheres to the carbon precursor and may cause a decrease in performance, which is not preferable. Also, if the pre-calcination temperature is too high, carbonization proceeds and the carbon precursor particles become too hard, and when pulverizing after pre-firing, pulverization may be difficult, such as scraping the inside of the pulverizer. Therefore, it is not preferable.
Pre-baking is performed in an inert gas atmosphere, and examples of the inert gas include nitrogen and argon. Pre-baking can also be performed under reduced pressure, for example, 10 kPa or less. The pre-baking time is not particularly limited, but can be performed, for example, in 0.5 to 10 hours, and more preferably 1 to 5 hours.

In the pre-firing of a carbon precursor with a butanol true density of 1.55 to 1.75 g / cm ³ , a large amount of tar is generated. Will be fused. Therefore, when pre-baking a carbon precursor having a butanol true density of 1.55 to 1.75 g / cm ³ , it is desirable to make the temperature increase rate of the pre-baking moderate. For example, the rate of temperature rise is preferably 5 ° C./h or more and 300 ° C./h or less, more preferably 10 ° C./h or more and 200 ° C./h or less, and further preferably 20 ° C./h or more and 100 ° C./h or less.

(Crushing process)
The pulverization step is performed in order to make the particle size of the carbon precursor uniform. It can also grind | pulverize after carbonization by this baking. As the carbonization reaction proceeds, the carbon precursor becomes hard and it becomes difficult to control the particle size distribution by pulverization. Therefore, the pulverization step is preferably performed after preliminary calcination and before main calcination.
The pulverizer used for pulverization is not particularly limited, and for example, a jet mill, a ball mill, a hammer mill, or a rod mill can be used.
Examples of classification include classification with a sieve, wet classification, and dry classification. Examples of the wet classifier include a classifier using a principle such as gravity classification, inertia classification, hydraulic classification, or centrifugal classification. Examples of the dry classifier include a classifier using the principle of sedimentation classification, mechanical classification, or centrifugal classification.

In the pulverization step, pulverization and classification can be performed using one apparatus. For example, pulverization and classification can be performed using a jet mill having a dry classification function.
Furthermore, an apparatus in which the pulverizer and the classifier are independent can be used. In this case, pulverization and classification can be performed continuously, but pulverization and classification can also be performed discontinuously.

(Main firing process)
The main firing step in the present invention can be performed according to a normal main firing procedure, and a carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode can be obtained by performing the main firing. The firing temperature is 900 to 1600 ° C. If the main calcination temperature is less than 900 ° C., many functional groups remain in the carbonaceous material and the H / C value becomes high, and the irreversible capacity increases due to reaction with lithium, which is not preferable. The lower limit of the main firing temperature of the present invention is 900 ° C. or higher, more preferably 1000 ° C. or higher, and particularly preferably 1100 ° C. or higher. On the other hand, if the main firing temperature exceeds 1600 ° C., the selective orientation of the carbon hexagonal plane increases and the discharge capacity decreases, which is not preferable. The upper limit of the main calcination temperature of the present invention is 1600 ° C. or less, more preferably 1500 ° C. or less, and particularly preferably 1450 ° C. or less.
The main firing is preferably performed in a non-oxidizing gas atmosphere. Examples of the non-oxidizing gas include helium, nitrogen, and argon, and these can be used alone or in combination. Furthermore, the main calcination can be performed in a gas atmosphere in which a halogen gas such as chlorine is mixed with the non-oxidizing gas. Moreover, this baking can also be performed under reduced pressure, for example, can also be performed at 10 kPa or less. Although the time for the main baking is not particularly limited, it can be performed, for example, in 0.1 to 10 hours, preferably 0.2 to 8 hours, and more preferably 0.4 to 6 hours.

(Manufacture of carbonaceous material from tar or pitch)
An example is given and demonstrated below about the manufacturing method of the carbonaceous material of this invention from a tar or a pitch.
First, the tar or pitch was subjected to a crosslinking treatment (infusibilization). The tar or pitch subjected to the crosslinking treatment is carbonized by subsequent firing to become a carbonaceous material whose structure is controlled.
Tar or pitch includes petroleum tar or pitch replicated during ethylene production, coal tar produced during coal carbonization, heavy component or pitch obtained by distilling off low boiling components of coal tar, tar or pitch obtained by liquefaction of coal Oil or coal tar or pitch can be used. Two or more of these tars and pitches may be mixed.

Specifically, as a method for the crosslinking treatment, there are a method using a crosslinking agent, a treatment with an oxidizing agent such as air, and the like. When using a cross-linking agent, a carbon precursor is obtained by adding a cross-linking agent to petroleum tar or pitch, or coal tar or pitch and heating and mixing to proceed with a cross-linking reaction. For example, as the crosslinking agent, polyfunctional vinyl monomers such as divinylbenzene, trivinylbenzene, diallyl phthalate, ethylene glycol dimethacrylate, or N, N-methylenebisacrylamide that undergo a crosslinking reaction by radical reaction can be used. The crosslinking reaction with the polyfunctional vinyl monomer is started by adding a radical initiator. As the radical initiator, α, α ′ azobisisobutyronitrile (AIBN), benzoyl peroxide (BPO), lauroyl peroxide, cumene hydroperoxide, 1-butyl hydroperoxide, hydrogen peroxide, or the like can be used. .

Also, when the crosslinking reaction is advanced by treatment with an oxidizing agent such as air, it is preferable to obtain a carbon precursor by the following method. That is, to a petroleum pitch or coal pitch, a bicyclic to tricyclic aromatic compound having a boiling point of 200 ° C. or higher or a mixture thereof is added as an additive and heated and mixed, and then molded to obtain a pitch molded body. Next, the additive is extracted and removed from the pitch molded body with a solvent having low solubility with respect to pitch and high solubility with respect to the additive to form a porous pitch, which is then oxidized with an oxidizing agent, and then carbon precursor. Get the body. The purpose of the aromatic additive is to extract and remove the additive from the molded pitch molded body to make the molded body porous, to facilitate crosslinking treatment by oxidation, and to obtain a carbonaceous material obtained after carbonization. To make it porous. As said additive, it can select from 1 type, or 2 or more types of mixtures, such as naphthalene, methyl naphthalene, phenyl naphthalene, benzyl naphthalene, methyl anthracene, phenanthrene, or biphenyl, for example. The amount of the aromatic additive added to the pitch is preferably in the range of 30 to 70 parts by mass with respect to 100 parts by mass of the pitch.

* Mixing of pitch and additives is performed in a molten state by heating in order to achieve uniform mixing. The mixture of the pitch and the additive is preferably performed after being formed into particles having a particle diameter of 1 mm or less so that the additive can be easily extracted from the mixture. Molding may be performed in a molten state, or may be performed by a method such as pulverizing the mixture after cooling. Solvents for extracting and removing the additive from the mixture of pitch and additive include aliphatic hydrocarbons such as butane, pentane, hexane, or heptane, mixtures mainly composed of aliphatic hydrocarbons such as naphtha or kerosene, methanol, Aliphatic alcohols such as ethanol, propanol or butanol are preferred. By extracting the additive from the pitch and additive mixture molded body with such a solvent, the additive can be removed from the molded body while maintaining the shape of the molded body. At this time, it is presumed that a through hole for the additive is formed in the molded body, and a pitch molded body having uniform porosity is obtained.

In order to crosslink the resulting porous pitch, it is then oxidized with an oxidizing agent, preferably at a temperature of 120 to 400 ° C. As the oxidizing agent, O ₂ , O ₃ , NO ₂ , a mixed gas obtained by diluting these with air, nitrogen, or the like, or an oxidizing gas such as air, or an oxidizing liquid such as sulfuric acid, nitric acid, or hydrogen peroxide water is used. be able to. It is simple and economical to oxidize at 120 to 400 ° C. and carry out a crosslinking treatment using a gas containing oxygen such as air or a mixed gas of air and other gas such as combustion gas as an oxidizing agent. Is also advantageous. In this case, if the pitch has a low softening point, the pitch melts during oxidation, making it difficult to oxidize. Therefore, the pitch used preferably has a softening point of 150 ° C. or higher.
The carbon precursor subjected to the crosslinking treatment as described above is pre-fired and then carbonized at 900 ° C. to 1600 ° C. in a non-oxidizing gas atmosphere to obtain the carbonaceous material of the present invention. Can do.

(Manufacture of carbonaceous material from resin)
A method for producing a carbonaceous material from a resin will be described below with an example.
The carbonaceous material of the present invention can also be obtained by carbonizing at 900 ° C. to 1600 ° C. using a resin as a precursor. As the resin, a phenol resin, a furan resin, or the like, or a thermosetting resin obtained by partially modifying the functional group of these resins can be used. It can also be obtained by pre-calcining the thermosetting resin at a temperature lower than 900 ° C., if necessary, pulverizing, and carbonizing at 900 ° C. to 1600 ° C. For the purpose of accelerating the curing of the thermosetting resin, accelerating the degree of crosslinking, or improving the carbonization yield, an oxidation treatment may be performed at a temperature of 120 to 400 ° C. as necessary. As the oxidizing agent, O ₂ , O ₃ , NO ₂ , a mixed gas obtained by diluting these with air, nitrogen, or the like, or an oxidizing gas such as air, or an oxidizing liquid such as sulfuric acid, nitric acid, or hydrogen peroxide water is used. be able to.
Furthermore, a carbon precursor obtained by crosslinking a thermoplastic resin such as polyacrylonitrile or a styrene / divinylbenzene copolymer can also be used. In these resins, for example, a monomer mixture obtained by mixing a radically polymerizable vinyl monomer and a polymerization initiator is added to an aqueous dispersion medium containing a dispersion stabilizer and suspended by stirring to suspend the monomer mixture into fine droplets. Then, it can be obtained by proceeding radical polymerization by raising the temperature. The obtained resin can be made into a spherical carbon precursor by developing a crosslinked structure by a crosslinking treatment. The crosslinking treatment can be performed in a temperature range of 120 to 400 ° C., particularly preferably 170 to 350 ° C., and more preferably 220 to 350 ° C. As the oxidizing agent, O ₂ , O ₃ , SO ₃ , NO ₂ , a mixed gas obtained by diluting these with air, nitrogen, or the like, or an oxidizing gas such as air, or an oxidizing property such as sulfuric acid, nitric acid, hydrogen peroxide water, or the like Liquid can be used. Thereafter, the carbon precursor that is infusible to heat as described above is pre-fired as necessary, and then pulverized and carbonized at 900 ° C. to 1600 ° C. in a non-oxidizing gas atmosphere, The carbonaceous material of the present invention can be obtained.
Although the pulverization step can be performed after carbonization, since the carbon precursor becomes hard as the carbonization reaction proceeds, it becomes difficult to control the particle size distribution by pulverization. It is preferable before the main baking later.

[2] Nonaqueous electrolyte secondary battery negative electrode The nonaqueous electrolyte secondary battery negative electrode of the present invention contains the carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode of the present invention.

In the negative electrode of the present invention, the electrode density is preferably 1.02 g / cm ³ or more, more preferably 1.04 g / cm ³ or more, from the viewpoint of further improving input / output characteristics.

In the negative electrode of the present invention, it is preferable that the average thickness is thin, specifically, it may be 60 μm or less in that the disadvantage of suppressing lithium migration that may be caused by insufficient gaps between particles due to close packing is suppressed. . On the other hand, if the average thickness is too small, the maximum particle size of the required carbonaceous material becomes low, and there is a concern about the difficulty of pulverization conditions to achieve it and the increase in ultrafine powder. For this reason, the average thickness may be 10 μm or more.

(Manufacture of negative electrode)
In the negative electrode using the carbonaceous material of the present invention, a binder (binder) is added to the carbonaceous material, and an appropriate solvent is added and kneaded to form an electrode mixture. It can be produced by pressure molding after coating and drying. By using the carbonaceous material of the present invention, it is possible to produce an electrode having high conductivity without adding a conductive auxiliary agent. When preparing the agent, a conductive aid can be added. As the conductive assistant, conductive carbon black, vapor grown carbon fiber (VGCF), nanotube, etc. can be used, and the amount added varies depending on the type of conductive assistant used, but the amount added is too small. Since the expected conductivity cannot be obtained, it is not preferable, and too much is not preferable because the dispersion in the electrode mixture becomes worse. From such a point of view, the preferable ratio of the conductive auxiliary agent to be added is 0.5 to 10% by mass (where the amount of active material (carbonaceous material) + the amount of binder + the amount of conductive auxiliary agent = 100% by mass). More preferably, it is 0.5 to 7% by mass, particularly preferably 0.5 to 5% by mass. The binder is not particularly limited as long as it does not react with an electrolytic solution such as PVDF (polyvinylidene fluoride), polytetrafluoroethylene, and a mixture of SBR (styrene-butadiene rubber) and CMC (carboxymethylcellulose). Among them, PVDF is preferable because PVDF attached to the surface of the active material hardly inhibits lithium ion migration and obtains favorable input / output characteristics. In order to dissolve PVDF and form a slurry, a polar solvent such as N-methylpyrrolidone (NMP) is preferably used, but an aqueous emulsion such as SBR or CMC can also be dissolved in water. When the amount of the binder added is too large, the resistance of the obtained electrode is increased, which is not preferable because the internal resistance of the battery is increased and the battery characteristics are deteriorated. Moreover, when there is too little addition amount of binder, the coupling | bonding with negative electrode material particle | grains and a collector is insufficient, and it is unpreferable. The amount of the binder added is preferably 3 to 13% by mass, more preferably 3 to 10% by mass for the PVDF binder, although it varies depending on the type of binder used. On the other hand, a binder using water as a solvent is often used by mixing a plurality of binders such as a mixture of SBR and CMC, and the total amount of all binders used is preferably 0.5 to 5% by mass. The amount is preferably 1 to 4% by mass. The electrode active material layer is basically formed on both sides of the current collector plate, but may be on one side if necessary. A thicker electrode active material layer is preferable for increasing the capacity because fewer current collector plates and separators are required. However, the larger the electrode area facing the counter electrode, the better the input / output characteristics, and the thicker the active material layer. Too much is not preferable because the input / output characteristics deteriorate.

The electrode density of the negative electrode can be adjusted by adjusting the pressing pressure. Since the negative electrode of the present invention preferably has a high electrode density, the pressing pressure may typically be 5.2 MPa (1.0 tf / cm ² ) or more. On the other hand, an excessively high press pressure is not preferable because the curvature of the electrode increases. 52.0 MPa (10.0 tf / cm ² ) or less is preferable, and 41.6 MPa (8.0 tf / cm ² ) or less is more preferable.

[3] Nonaqueous electrolyte secondary battery The nonaqueous electrolyte secondary battery of the present invention includes the negative electrode of the nonaqueous electrolyte secondary battery of the present invention.

(Manufacture of non-aqueous electrolyte secondary batteries)
When the negative electrode material of the present invention is used to form a negative electrode of a nonaqueous electrolyte secondary battery, other materials constituting the battery such as a positive electrode material, a separator, and an electrolytic solution are not particularly limited, and are nonaqueous solvents. Various materials conventionally used or proposed as a secondary battery can be used.

For example, as the positive electrode material, a layered oxide system (represented as LiMO ₂ , where M is a metal: for example, LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , or LiNi _x Co _y Mo _z O ₂ (where x, y and z represent composition ratios), olivine system (represented by LiMPO ₄ , M is metal: for example, LiFePO _4, etc.), spinel system (represented by LiM ₂ O ₄ , M is a metal: for example, LiMn ₂ O _4, etc. The composite metal chalcogen compound is preferable, and these chalcogen compounds may be mixed if necessary.These positive electrode materials are molded together with an appropriate binder and a carbon material for imparting conductivity to the electrode, and are electrically conductive. The positive electrode is formed by forming a layer on the conductive current collector.

The nonaqueous solvent electrolyte used in combination of these positive electrode and negative electrode is generally formed by dissolving an electrolyte in a nonaqueous solvent. Examples of the non-aqueous solvent include organic solvents such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, dimethoxyethane, diethoxyethane, γ-butyllactone, tetrahydrofuran, 2-methyltetrahydrofuran, sulfolane, or 1,3-dioxolane. These can be used alone or in combination of two or more. As the electrolyte, LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiAsF ₆ , LiCl, LiBr, LiB (C ₆ H ₅ ) ₄ , or LiN (SO ₃ CF ₃ ) ₂ is used. In secondary batteries, the positive electrode layer and the negative electrode layer formed as described above are generally immersed in an electrolytic solution with a liquid-permeable separator made of nonwoven fabric or other porous material facing each other as necessary. It is formed by. As the separator, a non-woven fabric usually used for a secondary battery or a permeable separator made of another porous material can be used. Alternatively, a solid electrolyte made of a polymer gel impregnated with an electrolytic solution can be used instead of or together with the separator.

The lithium ion secondary battery of the present invention is suitable as a battery (typically a lithium ion secondary battery for driving a vehicle) mounted on a vehicle such as an automobile.

The vehicle according to the present invention can be targeted without particular limitation, such as a vehicle normally known as an electric vehicle, a hybrid vehicle with a fuel cell or an internal combustion engine, and at least a power supply device including the battery, An electric drive mechanism that is driven by power supply from the power supply device and a control device that controls the electric drive mechanism are provided. Further, a power generation brake or a regenerative brake may be provided, and a mechanism for converting the energy generated by braking into electricity and charging the lithium ion secondary battery may be provided. Since the hybrid vehicle has a particularly low degree of freedom in battery volume, the battery of the present invention is useful.

Hereinafter, the present invention will be specifically described by way of examples, but these do not limit the scope of the present invention.

The physical property values (ρ _Bt , BET specific surface area, number average particle size, volume average particle size (D _v50 ), cumulative volume particle size D _v10 and D _{v90 of the} carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode of the present invention are shown below. , Hydrogen / carbon atomic ratio (H / C), d ₀₀₂ , charge capacity, discharge capacity, irreversible capacity, input characteristics, electrode density) are described in this specification including examples. The physical property values to be described are based on values obtained by the following method.

(True density by the butanol method (ρ _Bt ))
The true density was measured by a butanol method according to a method defined in JIS R 7212. The mass (m ₁ ) of a specific gravity bottle with a side tube having an internal volume of about 40 mL is accurately measured. Next, the sample is placed flat on the bottom so as to have a thickness of about 10 mm, and its mass (m ₂ ) is accurately measured. Gently add 1-butanol to this to a depth of about 20 mm from the bottom. Next, light vibration is applied to the specific gravity bottle, and it is confirmed that large bubbles are not generated. Then, the bottle is placed in a vacuum desiccator and gradually evacuated to 2.0 to 2.7 kPa. Keep at that pressure for 20 minutes or more, and after the generation of bubbles has stopped, take it out, fill it with 1-butanol, plug it and immerse it in a constant temperature water bath (adjusted to 30 ± 0.03 ° C) for 15 minutes or more. Adjust the liquid level of 1-butanol to the marked line. Next, this is taken out, the outside is well wiped off and cooled to room temperature, and then the mass (m ₄ ) is accurately measured.

Next, the same specific gravity bottle is filled with only 1-butanol, immersed in a constant temperature water bath as described above, and after aligning the marked lines, the mass (m ₃ ) is measured. Moreover, distilled water excluding the gas that has been boiled and dissolved immediately before use is collected in a specific gravity bottle, immersed in a constant temperature water bath in the same manner as described above, and after aligning the marked line, the mass (m ₅ ) is measured. ρ _Bt is calculated by the following equation.

At this time, d is the specific gravity (0.9946) of water at 30 ° C.

(Specific surface area by nitrogen adsorption (SSA))
An approximate expression derived from the BET expression is described below.

Using the above approximate expression, at liquid nitrogen temperature, 1-point method by nitrogen adsorption seek v _m by (relative pressure x = 0.2), was calculated a specific surface area of the sample by the following equation.

In this case, _{v m} is the adsorption amount necessary for forming a monomolecular layer on the surface of the sample ^(cm 3 / g), v the adsorption amount of the measured ^(cm 3 / g), x is a relative pressure.

Specifically, using a “Flow Sorb II2300” manufactured by MICROMERITICS, the amount of nitrogen adsorbed on the carbonaceous material at the liquid nitrogen temperature was measured as follows. Fill the sample tube with a carbonaceous material pulverized to a particle size of about 1 to 7 μm, and cool the sample tube to -196 ° C while flowing a mixed gas of helium: nitrogen = 80:20 to adsorb nitrogen to the carbonaceous material. Let The sample tube is then returned to room temperature. At this time, the amount of nitrogen desorbed from the sample was measured with a thermal conductivity detector, and the amount of adsorbed gas v was obtained.

(Atomic ratio of hydrogen / carbon (H / C))
Measurement was performed in accordance with the method defined in JIS M8819. From the mass ratio of hydrogen and carbon in the sample obtained by elemental analysis with a CHN analyzer, the hydrogen / carbon atom number ratio was obtained.

(Average layer surface spacing by X-ray diffraction method (d ₀₀₂ ))
The carbonaceous material powder was filled in the sample holder and measured by a symmetrical reflection method using X'Pert PRO manufactured by PANalytical. The scanning range was 8 <2θ <50 °, and the applied current / applied voltage was 45 kV / 40 mA. An X-ray diffraction pattern was obtained using a CuKα ray (λ = 1.5418Å) monochromated by a Ni filter as a radiation source. . Correction was performed using the diffraction peak of the (111) plane of the high-purity silicon powder for standard substances. The wavelength of the CuKα ray is set to 0.15418 nm, and d ₀₀₂ is calculated by the Bragg formula.

λ: X-ray wavelength, θ: diffraction angle

(Volume average particle diameter _{(D v50} by laser diffraction method), the cumulative volume particle diameter _{(Dv 10, D v90)}
Three drops of a dispersing agent (cationic surfactant “SN Wet 366” (manufactured by San Nopco)) are added to about 0.01 g of the sample, and the dispersing agent is acclimated to the sample. Next, after adding pure water and dispersing with ultrasonic waves, a particle size distribution in the range of 0.02 to 2000 μm was obtained with a particle size distribution measuring instrument (“Microtrac MT3300EX” manufactured by Nikkiso Co., Ltd.). Under the measurement conditions, the permeability was absorption, the particle refractive index was 1.81, and the shape was non-spherical. From the obtained particle size distribution, the volume average particle size _Dv50 is _{defined as the} particle size at which the volume-based cumulative volume is 50%. Further, the particle size of which cumulative volume is 90% and _{D v90,} the particle size of which cumulative volume of 10% was _{D v10.}
The amount of particles having a volume particle diameter of 30 μm or more was calculated by subtracting from 100 the cumulative value up to the measured volume particle diameter of 30 μm.

(Number average particle diameter)
The number average particle size was determined by the particle size at which the cumulative volume based on the number was 50% by the same method as described above.

(Active material dope-dedope test)
Using the carbonaceous materials 1 to 10 and the comparative carbonaceous materials 1 to 3 obtained in Examples 1 to 10 and Comparative Examples 1 to 5, the following operations (a) to (d) were performed, and the negative electrode and A non-aqueous electrolyte secondary battery was fabricated and the electrode performance was evaluated.

(A) Electrode preparation NMP was added to 94 parts by mass of the carbonaceous material and 6 parts by mass of polyvinylidene fluoride (“KF # 9100” manufactured by Kureha Co., Ltd.) to form a paste, which was uniformly applied on the copper foil. After drying, it was punched out into a disk shape having a diameter of 15 mm from a copper foil, and this was pressed at 2.5 tf / cm ² (13 MPa) to obtain an electrode. The amount of the carbonaceous material in the electrode was adjusted to about 9 mg.

(Electrode density)
The negative electrode is obtained by applying a mixture of a carbonaceous material with a binder having a mass ratio of P on a current collector having a thickness of t1 [cm] and a mass per unit area of W1 [g / cm ² ]. The negative electrode having a thickness of t2 [cm] manufactured by pressurization was punched with a predetermined area S [cm ² ], and the mass of the negative electrode after punching was set to W2 [g]. At this time, the electrode density was calculated as follows.
Electrode density [g / cm ³ ] = (W2 / S−W1) / (t2−t1)

(Average thickness)
The thickness of the negative electrode active material layer corresponds to half of the thickness obtained by subtracting the thickness of the current collector from the negative electrode when the negative electrode active material layers are present on both sides of the current collector of the negative electrode. Further, when the negative electrode active material layer exists only on one side of the current collector, this corresponds to a thickness obtained by subtracting the thickness of the current collector from the negative electrode. Specifically, the thickness of the negative electrode active material and the current collector was measured with a thickness measuring machine. Measurements were taken at five locations, and the average value was taken as the average thickness.

(B) Production of test battery The carbonaceous material of the present invention is suitable for constituting the negative electrode of a non-aqueous electrolyte secondary battery, but the discharge capacity (de-doping amount) and irreversible capacity (non-desorption) of the battery active material. In order to accurately evaluate the amount of doping) without being affected by variations in the performance of the counter electrode, a lithium secondary battery is configured using the electrode obtained above, using lithium metal with stable characteristics as a counter electrode, Its characteristics were evaluated.

The lithium electrode was prepared in a glove box in an Ar atmosphere. A 16 mm diameter stainless steel mesh disk is spot-welded to the outer lid of a 2016 coin-sized battery can, and then a 0.8 mm thick metal lithium sheet is punched into a 15 mm diameter disk shape. To be an electrode (counter electrode).

Using the electrode pair thus produced, the electrolyte solution was LiPF ₆ at a ratio of 1.4 mol / L in a mixed solvent in which ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate were mixed at a volume ratio of 1: 2: 2. A coin-type non-aqueous electrolyte system of 2016 size in an Ar glove box using a polyethylene-made gasket as a separator, using a borosilicate glass fiber fine pore membrane having a diameter of 19 mm as a separator A lithium secondary battery was assembled.

(C) Measurement of battery capacity About the lithium secondary battery of the said structure, the charge / discharge test was done at 25 degreeC using the charge / discharge test apparatus ("TOSCAT" by Toyo System). Lithium doping reaction on the carbon electrode was performed by the constant current constant voltage method, and dedoping reaction was performed by the constant current method. Here, in a battery using a lithium chalcogen compound as a positive electrode, the lithium doping reaction to the carbon electrode is “charging”, and in a battery using a lithium metal as the counter electrode like the test battery of the present invention, This doping reaction is referred to as “discharge”, and the naming of the lithium doping reaction to the same carbon electrode differs depending on the counter electrode used. Therefore, for the sake of convenience, the lithium doping reaction on the carbon electrode will be described as “charging”. Conversely, “discharge” is a charging reaction in the test battery, but is referred to as “discharge” for convenience because it is a dedoping reaction of lithium from the carbonaceous material. The charging method adopted here is a constant current constant voltage method. Specifically, constant current charging was performed at 0.5 mA / cm ² until the terminal voltage reached 0.050 V, and the terminal voltage reached 0.050 V. Thereafter, constant voltage charging was performed at a terminal voltage of 0.050 V, and charging was continued until the current value reached 20 μA. At this time, the value obtained by dividing the supplied amount of electricity by the mass of the carbonaceous material of the electrode was defined as the charge capacity (mAh / g) per unit mass of the carbonaceous material. After completion of charging, the battery circuit was opened for 30 minutes and then discharged. The discharge was a constant current discharge at 0.5 mA / cm ² and the final voltage was 1.5V. A value obtained by dividing the quantity of electricity discharged at this time by the mass of the carbonaceous material of the electrode is defined as a discharge capacity (mAh / g) per unit mass of the carbonaceous material. The capacity per volume is calculated by multiplying the capacity per mass by the above electrode density. The irreversible capacity is calculated as charge capacity-discharge capacity. A test battery prepared using the same sample was measured three times (n = 3), and the measured values were averaged to determine the charge / discharge capacity and the irreversible capacity. Further, the initial efficiency (%) was obtained by multiplying the value obtained by dividing the discharge capacity by the charge capacity by 100. This is a value indicating how effectively the active material has been used.

(D) Input characteristics in 50% charged state For the negative electrode, a negative electrode was prepared in the same procedure as in (a) above. The amount of the carbonaceous material in the electrode was adjusted so as to have a prescribed electrode thickness after pressing. The positive electrode was made into a paste by adding NMP to 94 parts by mass of lithium cobaltate (LiCoO ₂ ), 3 parts by mass of carbon black, and 3 parts by mass of polyvinylidene fluoride (Kureha KF # 1300) and uniformly applied onto the aluminum foil. . After drying, the coated electrode was punched onto a disk having a diameter of 14 mm and pressed to obtain an electrode. Note that the amount of lithium cobalt oxide in the positive electrode was adjusted to be 95% of the charge capacity of the negative electrode active material. The capacity of lithium cobaltate was calculated as 150 mAh / g.
The electrode pair thus prepared was used, and the electrolyte was LiPF at a ratio of 1.4 mol / liter in a mixed solvent in which ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate were mixed at a volume ratio of 1: 2: 2. ₆ is added, a borosilicate glass fiber microporous membrane with a diameter of 19 mm is used as a separator, a polyethylene gasket is used, and a 2032 size coin-type nonaqueous electrolyte is used in an Ar glove box. -Based lithium secondary battery was assembled.

First, after performing aging by repeating charging and discharging twice at 25 ° C., an input / output test was started. The constant current and constant voltage conditions adopted in aging are such that the current value is charged at C / 5 until the battery voltage reaches 4.2 V during the first aging, and then the voltage is maintained at 4.2 V ( Charging is continued until the current value reaches C / 100 by continuously changing the current value (while maintaining a constant voltage). After completion of charging, the battery circuit was opened for 10 minutes and then discharged. Discharging was performed at a current value of C / 5 until the battery voltage reached 2.75V. The second aging was performed in the same manner as the first time except that the current value was set to 2C / 5. The discharge capacity at the second aging of 2 / 5C was defined as the initial capacity. The battery was charged to a charge depth of 50% with respect to the initial capacity, the test environment was set to −20 ° C. and sufficiently maintained, and then discharged in the order of 0.5 C, 1 C, and 2 C for 10 seconds alternately. From the relationship between the voltage and current in the first second when discharging at each current value, the current value when the upper limit voltage was 4.2 V was extrapolated, and the input value was calculated from the obtained upper limit voltage and current value. . The input density was calculated by dividing the input value by the volume of the positive electrode and the negative electrode. The -20 ° C input density ratio was calculated from the ratio with the input density obtained in the above input / output test at -20 ° C.

Tables 1 and 2 show the characteristics of the obtained lithium secondary battery.

Example 1
A 70 kg petroleum pitch with a softening point of 205 ° C. and an H / C atomic ratio of 0.65 and 30 kg of naphthalene are charged into a 300 liter pressure vessel equipped with a stirring blade and an outlet nozzle, and heated, melted and mixed at 190 ° C. After cooling to 80 to 90 ° C., the inside of the pressure vessel was pressurized with nitrogen gas, and the contents were extruded from the outlet nozzle to obtain a string-like molded body having a diameter of about 500 μm. Subsequently, this string-like molded body was pulverized so that the ratio (L / D) of the diameter (D) to the length (L) was about 1.5, and the obtained crushed material was heated to 93 ° C. The solution was poured into an aqueous solution in which 53% by mass of polyvinyl alcohol (saponification degree 88%) was dissolved, stirred and dispersed, and cooled to obtain a spherical pitch molded body slurry. After most of the water was removed by filtration, naphthalene in the pitch formed body was extracted and removed with n-hexane having a mass about 6 times that of the spherical pitch formed body. The porous spherical pitch thus obtained was heated to 240 ° C. while passing through heated air using a fluidized bed, oxidized at a temperature of 240 ° C. for 1 hour, and insoluble to heat. Spherical oxidized pitch was obtained.
Next, 7 kg of a porous spherical oxidation pitch is put into a vertical tubular furnace having a diameter of 130 mm, heated to 100 ° C./h up to 600 ° C. under a nitrogen gas flow, and kept at 600 ° C. for 1 hour to perform preliminary firing, A carbon precursor was obtained. The obtained carbon precursor was pulverized with a steam jet mill (Toyo High-Tech Co., Ltd.) to obtain a powdery carbon precursor having a number average particle size of 0.73 μm and a volume average particle size of 6.9 μm. Subsequently, 10 g of this powdery carbon precursor was put into a horizontal tubular furnace having a diameter of 100 mm, heated to 1200 ° C. at a heating rate of 250 ° C./h, held at 1200 ° C. for 1 hour, and subjected to main firing, Carbonaceous material 1 was prepared. The main firing was performed in a nitrogen atmosphere with a flow rate of 10 L / min.

(Example 2)
A carbonaceous material 2 was obtained in the same manner as in Example 1 except that a powdery carbon precursor having a number average particle size of 0.68 μm and a volume average particle size of 4.9 μm was used.

Example 3
A carbonaceous material 3 was obtained in the same manner as in Example 1 except that a powdery carbon precursor having a number average particle size of 0.59 μm and a volume average particle size of 2.8 μm was used.

Example 4
The oxidation temperature of the porous spherical pitch was changed to 270 ° C., the powder was pulverized with a counter jet mill (Hosokawa Micron Corporation / 100-AFG) at a rotational speed of 20000 rpm, and the fine powder collected by the bag filter was mixed to obtain a number average particle A carbonaceous material 4 was obtained in the same manner as in Example 1 except that a powdery carbon precursor having a diameter of 0.62 μm and a volume average particle diameter of 3.8 μm was used.

(Example 5)
A carbonaceous material 5 is obtained in the same manner as in Example 4 except that the oxidation temperature of the porous spherical pitch is 240 ° C. and that the powdery carbon precursor has a number average particle size of 0.67 μm and a volume average particle size of 3.8 μm. It was.

(Example 6)
The carbonaceous material 6 was changed in the same manner as in Example 4 except that the oxidation temperature of the porous spherical pitch was changed to 205 ° C. to obtain a powdery carbon precursor having a number average particle size of 0.62 μm and a volume average particle size of 3.7 μm. Got.

(Example 7)
The porous spherical pitch obtained by the same method as in Example 1 was heated to 190 ° C. while passing through heated air using a fluidized bed, oxidized at a temperature of 190 ° C. for 1 hour, and subjected to crosslinking treatment. A porous spherical oxide pitch was obtained. 200 g of the obtained porous spherical oxidation pitch was placed in a 150 mm horizontal tubular furnace, heated to 600 ° C. at 150 ° C./h, held at 600 ° C. for 1 hour, and pre-baked to obtain a carbon precursor. . The obtained carbon precursor was coarsely pulverized to a diameter of 2 mm or less, then pulverized by a counter jet mill (Hosokawa Micron Corporation / 100-AFG), and the fine powder collected by the bag filter was mixed to obtain a number average particle size of 0. It was set as the powdery carbon precursor of 55 micrometers and a volume average particle diameter of 3.2 micrometers. Subsequently, 10 g of this powdery carbon precursor was put into a horizontal tubular furnace having a diameter of 100 mm, heated to 1200 ° C. at a heating rate of 250 ° C./h, held at 1200 ° C. for 1 hour, and subjected to main firing, Carbonaceous material 7 was prepared. The main firing was performed in a nitrogen atmosphere with a flow rate of 10 L / min.

(Example 8)
The carbonaceous material 8 was prepared in the same manner as in Example 7 except that the oxidation time of the porous spherical pitch was changed to 7 min to obtain a powdery carbon precursor having a number average particle size of 0.53 μm and a volume average particle size of 3.1 μm. Got.

Example 9
A carbonaceous material 9 was obtained in the same manner as in Example 6 except that a powdery carbon precursor having a number average particle size of 0.53 μm and a volume average particle size of 4.6 μm was used.

(Example 10)
A coal pitch having a softening point of 188 ° C. and an H / C atomic ratio of 0.51 was pulverized by a counter jet mill (Hosokawa Micron Corporation / 100-AFG) at a rotational speed of 13000 rpm to obtain a powdery pitch having an average particle diameter of 5.2 μm. . Subsequently, the powdery pitch was put into a muffle furnace (Denken Co., Ltd.), and infusible treatment was performed by maintaining the air at 280 ° C. for 1 hour while circulating air at 20 L / min to obtain an infusible pitch. 100 g of the obtained infusible pitch was put in a crucible, heated at a rate of 50 ° C./h up to 600 ° C. in a vertical tubular furnace, held at 600 ° C. for 1 hour, pre-fired, and carbon precursor was Obtained. Pre-baking was performed in a nitrogen atmosphere with a flow rate of 5 L / min, and the crucible was opened. The obtained carbon precursor was pulverized by a sample mill to obtain a powdery carbon precursor having an average particle size of 4.6 μm. 10 g of powdered carbon precursor is put into a horizontal tubular furnace having a diameter of 100 mm, heated to 1200 ° C. at a temperature rising rate of 250 ° C./h, held at 1200 ° C. for 1 hour, and subjected to main firing to obtain carbonaceous material 10 Was prepared. The main firing was performed in a nitrogen atmosphere with a flow rate of 10 L / min.

(Comparative Example 1)
The precursor after pre-firing was pulverized by a ball mill and classified into fine powders to obtain a powdery carbon precursor having a number average particle size of 2.9 μm and a volume average particle size of 10.5 μm. A comparative carbonaceous material 1 was obtained.

(Comparative Example 2)
The pre-fired precursor is pulverized with a counter jet mill (Hosokawa Micron Corporation / 100-AFG) and classified into fine powders to obtain a powdery carbon precursor having a number average particle size of 2.7 μm and a volume average particle size of 6.5 μm. A comparative carbonaceous material 2 was obtained in the same manner as in Example 4 except that.

(Comparative Example 3)
A comparative carbonaceous material 3 was obtained in the same manner as in Example 2 except that a powdery carbon precursor having a number average particle size of 0.44 μm and a volume average particle size of 0.80 μm collected by the bag filter of Example 2 was used. It was.

(Comparative Example 4)
A comparative carbonaceous material 4 was obtained in the same manner as in Example 2 except that the firing temperature was changed to 800 ° C.

Tables 1 and 2 show the characteristics of the carbonaceous materials obtained in Examples and Comparative Examples, and the results of measurement and evaluation of the negative electrode produced using the carbonaceous materials and battery performance. Table 3 shows the results of measuring the input density using the carbonaceous material of Example 5 while changing the average thickness of the negative electrode.

The carbonaceous materials of Examples 1 to 10 are composed of small particles having a number average particle diameter in the range of 0.1 to 2.0 μm, and the number average particle diameter / volume average particle diameter is in the range of 0.3 or less. Thus, since it has such a broad particle size distribution, the filling property was improved, and a high discharge capacity per volume was obtained. This is also indicated by the high density of the electrodes pressed under the same pressing conditions. In addition, the input density in a low temperature environment has also been improved.
In contrast, the carbonaceous materials of Comparative Examples 1 to 3 do not satisfy the scope of the present invention in terms of the number average particle diameter and the number average particle diameter / volume average particle diameter. C does not satisfy the scope of the present invention. Therefore, the electrode density was lower than that of the example. Further, the discharge capacity per volume was lower than that of the example, and the initial efficiency or the input density under a low temperature environment tended to be inferior to that of the example. Thus, the examples satisfying the scope of the present invention had good input / output characteristics.

Claims (9)

1. The number average particle size is 0.1 to 2.0 μm, the value obtained by dividing the number average particle size by the volume average particle size is 0.3 or less, and the (002) plane average layer surface determined by the X-ray diffraction method A carbonaceous material for a negative electrode of a non-aqueous electrolyte secondary battery, wherein the distance d ₀₀₂ is 0.340 to 0.390 nm, and the atomic ratio (H / C) of hydrogen and carbon is 0.10 or less.
2. The carbonaceous material for a negative electrode of a nonaqueous electrolyte secondary battery according to claim 1, _{wherein the} volume average particle diameter _Dv50 is 1 to 7 µm.
3. The carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode according to claim 1 or 2, wherein a cumulative volume particle diameter _Dv10 is 2.5 µm or less.
4. The carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode according to any one of claims 1 to 3, wherein the amount of particles having a volume particle diameter of 30 µm or more is 1.0 vol% or less.
5. A negative electrode for a non-aqueous electrolyte secondary battery comprising the carbonaceous material for a non-aqueous electrolyte secondary battery negative electrode according to any one of claims 1 to 4.
6. The negative electrode for a nonaqueous electrolyte secondary battery according to claim 5, wherein the electrode density is 1.02 g / cm ³ or more when a pressing pressure of 13 MPa (2.5 tf / cm ² ) is applied.
7. The negative electrode for a nonaqueous electrolyte secondary battery according to claim 5 or 6, wherein the average thickness is 60 µm or less.
8. A nonaqueous electrolyte secondary battery comprising the negative electrode for a nonaqueous electrolyte secondary battery according to any one of claims 5 to 7.
9. A vehicle equipped with the nonaqueous electrolyte secondary battery according to claim 8.